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Solar system with seven Earth-sized exoplanets ()downtoearth, )

The National Aeronautics and Space Administration (NASA) announced on February 23 the discovery of a solar system with seven Earth-sized exoplanets about 39 light years away from our sun. The discovery is being seen as very significant as the planets found orbiting dwarf star TRAPPIST-1 could potentially harbour life.

NASA has called the newly discovered solar system a ‘sister solar system’ to our own. The dwarf star TRAPPIST-1 is a low-mass, dim, ultracool star (with an effective temperature under 2,430 degrees Celsius) in the Aquarius constellation. All seven planets, apparently, have earth-like masses and could potentially host liquid water- considered a critical factor for the existence of life. While the presence of water largely depends on other properties of the planets, six of the inner planets are thought to be made up of rock and having surface temperatures ranging from 0-100 degrees Celsius, deemed conducive for life.

The TRAPPIST-1 solar system is a compact system in which the innermost planet takes about 1.5 days to orbit the sun while the sixth planet takes 13. Earth takes 365 days to complete the same journey around our sun. The seventh planet is the least observed and has been seen to orbit the star just once thus far. Three of the planets fall in the conventional “habitable zone” of the solar system, but due to the compact nature of the system and the low temperature of the star, scientists believe that even the farthest planet could host liquid water and extra-terrestrial life if it has an atmosphere that traps heat effectively.

The compact nature of the solar system could also have other effects.

Three of the planets fall in the conventional “habitable zone” of the solar system. Credit: NASA/JPL-Caltech
Three of the planets fall in the conventional “habitable zone” of the solar system. Credit: NASA/JPL-Caltech

The dwarf star is comparable to Jupiter in our own solar system and the entire system is reminiscent of Jupiter and its moons in our own solar system. It is thought that planets might be affected by the star and each other due to proximity. One of the effects that is being investigated now is that of tidal locking where the celestial body’s orbital period matches its rotational period. This is commonly seen on the moons of Jupiter as well as our own moon where the moon takes 28 days both to move around the earth as well as to rotate on its own axis.

This would imply that one face of the planets would be constantly facing the star while the other side would constitute the “dark side” of the planets. So, while one side is constantly hot, the other could be devoid of direct heat from the star and this could do some strange things to the temperature profiles and gradients of the planet.

Although the initial indications are promising, scientists maintain that the discovery of the potentially for life in solar system does not automatically mean the presence of water or life and that there is a lot that remains to be ascertained about the system like the atmospheric composition of the planets.

Earth-sized exoplanets are speculated to be several in number in the galaxy. The past few years have seen a number of newly discovered exo-planets that resemble our home planet although discovery itself is simply the first step in the search for habitable and inhabitated planets. The focus now is going to be on studying the conditions prevalent in the TRAPPIST-1 system.

Back in 2014, Kepler 186f became the first validated Earth-size planet in the habitable zone of another star. The next year, the NASA discovered a six billion-year-old planet, named Kepler 452B. The planet so closely resembled its cousin Earth that it was basically “Earth 2.0”.

Earth 2.0: NASA finds planet's 'cousin'

NASA announced the discovery of a planet in the Milky Way galaxy, 1400 light years away. The discovery is believed to be the closest to Earth so far.

In a press conference to announce the discovery of the exoplanet, John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington, said the planet so closely resembled its cousin Earth that it was basically “Earth 2.0”.

The six billion-year-old planet, named Kepler 452B, was found to be 1.5 times the size of Earth and is likely to have a rocky surface. Jon Jenkins, a Kepler lead analyst at NASA revealed that the planet was at the right distance from the sun to support life and that it had an orbit that was similar to Earth with a 385-day year range. Jenkins added that the newly-discovered exoplanet received 10 per cent more energy from its star and had spent billions of years in the “goldilock’s zone” or habitable zone in its solar system, which means it could very well be habituated by life.

The discovery was made by the Kepler space observatory and was confirmed by the Hubble telescope and other Earth-based observatories. The spacecraft Kepler monitors stars’ light and notices the dip in light to discover planets when they cross in front of the star.

Responding to a question, Jenkins said that it would likely be possible for humans to adapt to the gravity on Kepler 452B which is twice the gravity on Earth. Although Jeff Coughlin, Kepler research scientist at SETI Institute in Mountain View, California , later added that it might well be a few generations before we’re able to land on the planet.

For now, it looks like even getting a closer look from the surface of Kepler 452B will take a while. “Just the speed that a spacecraft could get there, even if was travelling near to the speed of light, would take many decades," said Coughlin in response to a question about getting a camera or probe on to the surface.

So far, there has been no evidence of life on the planet although Kepler could have possibly have life and could also support photosynthesis and plant life, claimed Jenkins.

We are now aware of 12 planets that could potentially support life out of the thousands of planets that have been discovered since the first one was discovered outside our solar system 20 years ago.

(The article was published on Down To Earth on July 23, 2015)

Most Earth-like planet yet spotted

Although the size of Kepler-186f is known, its mass and composition are not. (Photo credit: NASA)
Although the size of Kepler-186f is known, its mass and composition are not. (Photo credit: NASA)

There is exciting news for those looking for and wondering about potentially habitable planets outside our solar system. Scientists have discovered what they claim is the most Earth-like planet detected till date.

The planet, Kepler 186f, detected by NASA's orbiting Kepler telescope, is circling a red dwarf star, Kepler 186, some 500 light years away (one light year equals about 9.5 trillion km) and exists in the “Goldilocks zone” where it's neither too hot nor too cold. The planet, which is about 10 per cent larger than Earth, may very well have liquid water that makes life possible on Earth, scientists said. This is because it resides at the outer edge of the habitable temperature zone around its star — the sweet spot where lakes, rivers or oceans may exist without freezing solid or boiling away.

“Kepler 186f is the first validated, Earth-size planet in the habitable zone of another star,” said Elisa V Quintana of the SETI Institute and NASA’s Ames Research Center in Mountain View, California at a news conference on Thursday. “It has the right size and is at the right distance to have properties similar to our home planet.” Quintana said she considers the planet to be more of an "Earth cousin" than a twin because it circles a star that is smaller and dimmer than our sun. While Earth revolves around the sun in 365 days, this planet completes an orbit of its star every 130 days.

The diagram compares the planets of our inner solar system to Kepler-186 (Photo credit: NASA Ames/SETI)
The diagram compares the planets of our inner solar system to Kepler-186 (Photo credit: NASA Ames/SETI)

Kepler-186f is part of a system of five planets, all of which are roughly Earth's size. However, the other planets are too close to their star to support life.

Kepler 186f, named after NASA's Kepler planet finding mission, is too far away for astronomers to ascertain its mass, or if it has an atmosphere and supports life.

Kepler telescope examines Space for subtle changes in brightness that indicate an orbiting planet is crossing in front of a star. From those changes, scientists calculate a planet's size and make certain inferences about its makeup.

Since its launch in 2009, Kepler has confirmed 961 planets, but only a few dozen are in the habitable zone. Most are giant gas balls like Jupiter and Saturn, and not ideal places for life.


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